Marketing and Multiple Streams

We've all heard of the idea of multiple streams of income, if from no other source, then from Robert Allen's books on that topic. But what does it really mean to build multiple streams of income? What does it take, and can anyone do it? What's the process, and where should an Internet marketer start?
For many new marketers, the most common obstacle in their new business is just to get started. They will usually have an idea, whether for their own product or service or to work as an affiliate. They will buy ebooks, audios, software, study hosting plans, and so on, trying to learn everything they can. The trouble is, they can on doing those things and never actually do anything. There's nothing wrong with learning from various products, and there are certainly plenty of tempting marketing info-products available. But at some point, they actually have to do something.
Perhaps the second most common obstacle, and one that is hard for even veteran marketers to deal with, is difficulty in staying focused on one project, one goal, or one product. Marketers seem to be a curious lot, and by and large are naturally drawn to different paths of earning income, different marketing techniques, and yes, the latest info-product or software of the day. Even marketers who've gotten past the idea that one-click will make them rich still tend to fall into the habit of hopping between projects.
To truly understand what building multiples streams of income in Internet marketing is all about, let's carry the idea of to a real life analogy. Let's pretend we're farmers who need to irrigate our field so our crops will grow. These crops will both feed us, and provide us with an income since we can sell a portion of them. Nearby are several rivers, where water is plentiful. Step by step, what do we have to do?
First, we have to dig trenches in our field towards the river, so water will flow to where it's needed. Did you notice the digging part? That means work has to come first, before anything else happens. You can buy all the manuals you want on digging trenches, you can ask others what they've done, you can study trench-gurus, and those are good things to do. Learn from experience. But in the end, no trenches will appear until you dig.
But wait! Before you dig, isn't it important to know where you're going to dig? Would it make sense to put all of your trenches at one end of the field, or should you strategically plan them first, so they'll bring the most benefit to your crop with the least effort on your part?
By the way, shouldn't you also decide which river you're going to dig towards? You're not going to just start digging somewhere and see what happens, are you? No, you'll plan where your trenches go, and you'll also dig towards the river that makes the most sense for your field and crop. It should have a good water flow, with little potential of running dry, and should be fairly easy to find and reach. You don't want to dig towards a river that's miles away, that you've only heard about but never have seen do you?
Now, the key to everything. Are you going to dig a foot or two in one trench, then move on to another, then another, digging a little each time then starting over? Or would it be better to finish the first trench that will bring the most potential water? You could start a small part of your overall crop that is fed by water in the first trench. While it's growing, you can move on to the second trench, and so on. That seems like a better plan.
Finally, don't forget that you may run into rocks, clay, snakes, and other dangers in some places you dig. Just know that will happen sometimes, and find a new place to dig.